1. Field of the Invention
The present invention relates to an apparatus and method for controlling recording power in an optical drive, and more particularly, to an apparatus and method for controlling the optical recording power of a light emitting device so that the level of light output from the light emitting device is optimal for the type and recording multiple-speed (or referred to as multiple-speed) of optical media.
2. Description of the Related Art
Current optical media are roughly classified into optical media for compact disks (CDs) and optical media for digital versatile discs (DVDs). CD read (CD-R) and CD read/write (CD-RW) optical drives are widely used as optical drives for CDs. DVD-RW, DVD-R, DVD+RW and DVD-RAM optical drives are currently on the market as optical drives for DVDs. However, since optical media have different recording properties, they also have different shapes of recording pulses from one another.
For example, the recording pulse of a DVD-RAM or CD-RW can be defined as an on-start multi-pulse type since a multi-pulse train starts from a high state within a channel clock. In contrast, recording pulses of DVD+RW and DVD-R can be defined as an off-start multi-pulse type since a multi-pulse train starts from a low state within a channel clock. The recording pulse of a CD-R can be defined as a non-multi-pulse type since it is similar to a non-return to zero inverted (hereinafter referred to as NRZI) data without using multiple pulses.
Conventional methods have been developed to control the optical recording power of a laser diode (LD) for use as a light emitting device to generate a variety of shapes of recording pulses from a single optical drive. In the conventional optical recording power controlling apparatus and method, the optical recording power of a LD is controlled by considering the relationship between the size of a recording mark of received NRZI data and that of either of the spaces before and behind the recording mark. The optical recording power of the LD is also controlled by increasing or decreasing the optical output level reflected by an optical medium and detected by a photodiode used as a light receiving device to an optimal optical output level.
However, in the conventional optical recording power controlling apparatus and method, determining the optimal optical output level is limited to consideration of the relationship between the size of a recording mark of received NRZI data and that of either of the spaces before and behind the recording mark. The varying range of a recording power level is also limited as only the peak power level of a recording pulse varying in units of recording marks.
Thus, the conventional recording power controlling apparatus and method has a limit in adaptively controlling the optical recording power of an LD in order to meet the specifications of different types of optical media, including the recording multiple-speeds of optical media.